The Case for Matching Shaft with Self-Lubricating Bushings


A bushing design that experiences frequent start-ups and shut-downs can lead to premature wearing – or even failure. This also happens when a bushing runs too dry, for example when there is a sudden loss of contact lubrication, an aggressive contamination influence or simply an under-designed mating shaft.

During start-up, the shaft rubs against the bushing’s self-lubricating material. Typically the self-lubricating material is a polymer PTFE composite. The bushing polymer layer has inherent wear resistance developed by the manufacturer’s polymer material R&D efforts. This property of the bushing is influenced by the application condition and contacting shaft attributes.

Shaft material type, hardness, plating and roughness determine how the bushing will initially break-in and continue to run through useful life.

For the best performance in a self-lubricating bushing design, the complete bushing system should be closely reviewed to make sure that the shaft is designed correctly, and both the bushing and the shaft are genuinely service compatible. Meaning, the entire design allows for the bushing to easily reach its self- lubrication impact to the bearing system and stabilize progressing wear.

When this relationship is ignored, the bushing and shaft can become destructive of each other, promoting overheating conditions and a shorten life that shows as excess wear on the bushing surface. The shaft will also show signs of color change, galling or wear.

Self-lubricating bushings can handle frequent start-ups and shut-downs while providing efficient low wear and friction characteristics. Attention and proper care taken to the shaft design includes structural strength, material selection, surface hardness, finish and protective platings attributes. By following manufacturers design recommendations the complete bearing system will live to expectation.

A bushing manufacturer normally tests and evaluations their bushing material with different shaft conditions to satisfy an array of customer application uses. So, the manufacturer can provide useful input on how their product will perform under a variety of running conditions and shaft requirements. It makes sense to contact the bushing manufacturer’s technical department for help with your next bearing project.